94. CSI

Revenue: £45.8m

Another partner which likely features in this list for its final year after being acquired by Park Place Technologies, CSI Limited provides cloud, cyber security and data protection solutions, with a strong specialism in IBM Cloud and the Power platform. With a focus on supporting complex, regulated workloads, CSI has carved out a niche helping customers shift their most critical applications to hybrid, private and public cloud environments.

2023 was a transformative year for the business. In September, CSI underwent a major ownership change, with Cumulus Topco Ltd acquiring the group and installing a new leadership team. The shake-up brought a refreshed strategy, significant restructuring of the group’s cost base and a consolidated balance sheet that wiped out the bulk of historic debt. The result? A leaner, stronger business showing improved performance by the end of the year.

While group revenue dropped to £14.4m in 2023 — a decrease driven by weaker product sales — recurring income from managed services proved a steadying force. CSI posted an EBITDA of £5.7m for the year, in line with revised expectations. The firm also ended the year with a solid balance sheet, boasting £29.4m in assets and £13.9m in net current assets.

Over the past two years, CSI has invested heavily in modernising its infrastructure, platforms and workforce in response to the digital transformation boom that followed the Covid-19 pandemic. Although longer sales cycles and inflationary pressures posed challenges, the company’s high proportion of multi-year, contracted income has helped absorb the impact.

As an IBM Power specialist, CSI is also positioning itself to support customers adopting AI-enabled solutions built on the Power10 platform and IBM’s next-gen storage technology.